LONDON (Reuters) - GKN ( GKN.L ) faces pressure to open takeover talks with suitor Melrose Industries ( MRON.L ) from U.S. activist investor Elliott, which disclosed a stake in the British engineering company just days after it rejected a 7 billion pound ($9.66 billion) bid. Elliott, a hedge fund with a track record of intervening in takeovers, said on Monday that it holds a 1.7 percent interest in GKN through contracts-for-difference (CfDs)...